A primary concern in the health care environment is protecting the patient from infection whether endogenous, exogenous or nosocomial. One of the most common causes of hospital acquired infection arises from catheterization of the urinary tract. Even though the catheter is sterile, protecting the patient from exogenous infection, passage through the urethra to the bladder can transfer bacteria to the catheter which is then transmitted to the bladder. Other sources include the collection bag and periurethral area from which bacteria can migrate along the catheter into the bladder.
The problem is particularly prominent in long term catheterizations. Investigations have indicated that the risk of infection increases with each day of catheterization and that bacteriuria develops in almost 100 percent of chronically catheterized patients. In 1982 the Atlanta Center for Disease Control reported that approximately one-half million patients per year acquire urinary tract infections in acute care hospitals throughout the United States.
No sterile procedure known has been effective against preventing infections of this type. In an attempt to prevent infections otherwise the patient can be administered antibiotics systemically and prophylatically. While this provides some help, it is not totally effective; moreover, such methods are not without attendant problems. Another preventative step has been to apply antibacterial ointments to the shaft exterior of the catheter. However, this method provides only an initial surface treatment which is substantially removed during insertion leaving no protection for the patient with an indwelling catheter over long period of time.
One relatively recent method of controlling infections attendant the use of catheters is provided in U.S. Pat. No. 4,592,920. This patent is directed toward a method for producing antimicrobial catheters which includes the steps of suspending a comminuted antimicrobial metal compound in a curable suspending agent and then coating the catheter therewith. The suspension is then cured to bond it to the surface of the catheter. While a bonded coating is more permanent than a topical treatment with an ointment, it would be more desirable to provide as longer acting treatment by incorporation of the desired compound directly into the latex composition prior to curing.
The mere addition, however, is not satisfactory because the rubber latex can become destabilized preventing further manufacture of the particular additive does not remain intact during the manufacturing process or both. Of course incorporation, if successful, is of no benefit to the patient unless the desired compound can be brought to the surface of the article from within the rubber.
It is known that silicone is a material that can be compounded with rubber latex and will migrate from within the rubber to the surface. U.S. Pat. No. 3,962,519, for instance, provides for mixing silicone compounds directly into natural and synthetic rubber latex formulations prior to curing them relies upon the bleeding or migration of the silicone compound to the external surface of the instrument to provide resistance to unwanted adhesion and water repellency. The patent discloses employment of silicone compounds having a molecular weight of more than 90,000 and states that the amount present can range from about 0.1 to 10% by weight based upon the weight of the rubber. Of course, due to the migratory behavior of the silicone, the method of this patent does not permit relatively high amounts of silicone to be employed without causing separation of the silicone from the rubber latex and concomitant failure of the product.
U.S. Pat. No. 4,242,287 is directed toward an elastomeric composition comprising natural rubber latex and a silicone composition present in amounts of more than 10 to about 50 weight per 100 parts of rubber. The composition is stable and allows for continual migration of the silicone to the surface of the rubber. Articles, such as catheters, that are produced by multiple dip operations into the latex can be made without later separation of the layers.
Apart from the recognition that silicone could be incorporated into rubber compositions, there has been no incorporation of medication or other therapeutic agents into rubber compositions much less any suggestion to do so in these patents or within the existing state of the art.
Other rubber implements such as endo-tracheal tubes and rubber gloves must also be free from bacteria during use to protect exposed areas of the patient from bacterial and associated types of infection. Again, sterile procedures and topical antibacterial agents have not provided the answer.
Moreover, the threat of infectious diseases such as hepatitis, acquired immune deficiency syndrome, or AIDS, and the like have made the wearing of rubber gloves by health care workers, other than surgeons, necessary to protect the wearer. Likewise, condoms have always been proclaimed as an effective means of protecting against the spread of disease. In addition to the physical barrier provided by the rubber film, it is desirable to have incorporated into the foregoing articles various therapeutic agents that may be effective against the infectious microorganisms. While no drug has yet been found to be effective against AIDS, incorporation of such a compound into rubber gloves and condoms would be extremely helpful.